"Clicktophycin-52": a bioactive cryptophycin-52 triazole analogue.

An endocyclic trans-amide linkage within the macrocyclic antitumor agent cryptophycin-52 was replaced by a 1,4-disubstituted 1H-1,2,3-triazole ring. Macrocyclisation of the triazole analogue was accomplished by macrolactamization as well as by Cu(I)-mediated "click"-cyclization. Compared to cryptophycin-52, in vitro cytotoxicity of "clicktophycin-52" against the multidrug resistant human cancer cell line KB-V1 is only slightly reduced.